radiator STOCK Vs. KOYO?
 

anyone know which radiator is actually better? some numbers would be great. thanks

lol, you're joking, right?

the stock rad has plastic endtanks and looks like a runt next to the typically-used koyos

i know it sounds stupid but this is why i ask. i changed the stock rad to the koyo and i noticed that it took longer for the car to get to full temp but it ran a little bit hotter. i dont think my gauge just happen to break in between me changing the rad. what do you think? have any numbers?

copper or alum? and are we talking about both in the stock position?

I can't see, on paper, how the stock one could perform better, overall, than the koyo.

fwiw, I went from the stock rad in stock position, to twin core alum koyo, vertical, behind trust fmic (and with condensor sandwiched between) - and the cooling performance has so far been almost identical to what I got with the stock. However, the fan operation is now different due to tuning, so...

aluminum koyo. i have a front mount IC, but all i did was change the rad. the temp has gotten hotter after i changed it. i talked to 2 rotary specialists and they both couldnt give me an answer when i told them the story. however they said the stock rad was a good rad because of the fin design on the inside. im guessing the gauge is really bad. i dont want to put the stock rad back in to find out so i thought maybe someone on here would have some numbers.

so after the fans were modified what kind of readings were you getting?

with stock and koyo my cruising temp, on average, is/was about 89c - it was the same with the stock rad. However, the stock rad, under hot and heavy stop-start traffic, would rise to about 99c, sometimes 100, 101. Now it hits a max of 95, and the fans rapidly kick it back to sub-90.

I have some experience with both.

The koyo is nice; I currently have one in my car. But honestly I'm a pretty firm believer that the stock radiator works just fine end tanks aside. I ran the stock radiator behind an XS FMIC for two years without any cooling issues, just having the fans coming on early on the PFC. My temp sensor is in the T-stat housing and it was always around 185F with the factory radiator. Aside from WOT runs, where it would pretty much come down instantly after letting off. My temps are now the same with a Blitz FMIC and the koyo.

I'm curious to see how the combo works under hard driving. Since the car’s running last year’s stock twins 15psi tune. I can't really get into it and the it's running off the 7psi wastegate spring for now. However if I note anything worthwhile, I'll post it in the future.

thats awesome! thanks for everyones info!

FD4LIFE908,

Sometimes, bigger is not always better. If you are in racing conditions where your radiator is always getting air, then the bigger radiators are great. However, for normal street driving, you'll be holding more liquid in your larger radiator with less air hitting it. Add an FMIC in front of it and it's not all that great of an idea.

IMO, unless people are tracking their car, they should just get an aluminum stock replacement radiator. For street driving, there is no reason for a large radiator but several reasons why not.

I installed a Koyo last weekend. I've only driven the car once since then, but I noticed the temps when driving were significantly lower than they used to be. I was seeing on average 20-30 degree lower temps while in motion (~165-175 degrees). Of course as soon as I stopped moving, the temps climb rapidly up to the point the fans come on (~226 degrees I believe?). It was a cooler day (mid 60's) though, so that might have something to do with it. Thermostat is brand new OEM and the temps were measured at the tstat housing by a stewart warner gauge.

So who makes a straight aluminum stock replacement? The only ones I ever see people talking about are the koyo and the (enter name here i forgot). Sorry cannot remember the other one! I am going to change out my rad because the owner before me put in that leak sealent stuff and I want to get it out of my system. Sorry to hi-jack

-Bill

i dunno about you guys but i run a fmic and koyo rad and my heat range from 83-87 deg C even with WOT runs, depending on weather conditions. on insanely hot days in traffic i have seen it up to 91 tho. but by then i pull off the freeway and take sidestreets just to make sure i keep it moving.

This is without vented hood or heat wrapped downpipe. I plan on doing those things and hopefully it will keeps my temps down. and putting some fans on the intercooler to see if that helpsl.

Koyo, Fluidyne, Mazda Competition (available through some vendors), etc... Some of the vendors have had an aluminum (stock replacement) radiator manufactured for them as well or they sell someone else's knock-off radiator.

Joe

I have been intending to upgrade my stock radiator as part of the usual reliability modifications (I've pretty much done everything else) since buying the car but am having a hard time justifying it.

I have the PFC set to turn on the fans at 85C and it seems to absolutely prevent the temperature from going above that no matter the weather or how hard I am driving. I'm running 30% antifreeze, 70% distilled water and the usual bolt-ons (intake, y-pipe, SMIC, downpipe, high flow cat, exhaust). The only time I see higher than 85C is when I turn off the engine and let the car sit; when I start it again, the temperature rapidly returns to 85C.

I wonder if the plastic end tanks are a theoretical rather than a practical objection?

Ok, here is my $.02 on the matter.

FD4LIFE908,

You probably have air in your lines since you installed the Koyo.

Burp the system to get the air out.

Thank should improve your temperatures.

Fluidyne makes a pretty much stock replacement. Also, RadiatorWorld sells a direct stock aluminum replacement. There are also copper direct stock replacements. Copper is a better conductor of heat, but you sacrifce weight for heat exchange on something like that.


Unfortunately, people have had the plastic end tanks crack, just like the plastic AST.

taking a look at mazda's approach - they increased the size of the radiator in the final FD production runs, and then when you see an rx8 rad next to that, you can see that they went even bigger again.

The problem with the plastic end tanks is that they are prone to cracking, as Mahjik pointed out. Mine cracked.

The Koyo is thicker, so it might get less air flow through it under some conditions. It doesn't surprise me that it runs hotter sometimes. As long as it isn't "too hot", that is fine. The true test is at what point it overheats. I would expect the Koyo to have some additional headroom over the stock radiator when stressed.

-Max

i know i dont have air in the lines. i was running the car without a thermostat, either way it was out with both radiators and it was still hotter. anyway, the way to fix this overheating problem is to get a apexi power fc or a fan controller. hks makes one. or you could put a switch on your fans which will be a pain in the ass..

Umm...You know that the reason your car is heating up so slow is because you dont have a thermostat, right? Why complain about something that you caused?

Running without a T-stat is just plain dumb! Not only does it lengthen warm up excessively but it will actually lead to HIGHER temps, as removing the t-stat allows some of the coolant to completely bypass the radiator.

the temp was the same both ways that i noticed. thats why i never put it back in... i wasnt complaining, just trying to figure out some numbers

The fin design of the koyo is not the best. I noticed that after i installed it. Almost makes me want to switch radiators. But it still works. All most all production cars use plastic endtanks. I dont see a problme with them. They will out last the copper replacement radiators. The copper endtanks are bonded. And they fell more flimsy than the stock one. So if your factory radiator is still in good shape, i would keep it and just keep my eye on it. But if you want to replace it i would use a flyuidyne unit. I has a better design and is a bolt on. But it cost more.

The problem with the factory fd radiator is that it is way too small. the stock TII radiator is bigger then my koyo for my fd. Another problem with the fd radator is that you cant see it. Most cars you can see the top of the radiator, and thats where they usually leak. So on most cars you can see the plastic endtank begin to seep. But on a fd, you wont notice it untill it really leaks.

I would not run without a tstat. I run a stock tstat that i drill holes in. It helps bleed off any air pockets. I have my greddy coolant temp sending unit in the front of the tstat housing. So no, my gauge gets starts to read right away. Before it wont read and then go up to temp. The car literally takes about 30seconds longer to warm up.

I bought the koyo because it was cheaper. Most I do is auto x. It's held up well. I also did the FC thermoswitch. I'm happy. Old radiator was nasty. but it was 12 years old.

What a retard.